Zinc plate for Bolts and nuts exposed 1

[firsan64]

Hello, everybody.
There is inside Nace MR0175/ISO15156(2):2009; A2.1.5 a mention about the metalic coatings. That is a not acceptable for preventing SSC. For standard we offer the bolts and nuts to attend NAce with Zinc plated. The material is correct with Nace (B7M-2HM). Our intention is not preventing SSC. Could we provide plated or nude bolts and nuts ?

 

[Roberto1956]

I believe that you need a rusting prevention and I don't know the place of your construction or use. Anyway, only zinc plated is not satisfactory for marine enviroment. I prefer Zn-Ni for this case. In case of bolts and nuts the only problem is not corrosion resistance but abrasion resistance for the threads when you are bolting. Think about the disassembly of bolts and the plate status. There is a lot of methods that make me prefer Zn-Ni. See ASTM-B-850 that talks about the post heat treatment to avoid hydrogen embrittlement. If you provide no plated bolts and nuts but shot blasted and painted after the conclusion of the job you will have corrosion protection on the seen area but no protection on the others parts, so maybe it will be not a good solution and it depends of your enviroment.

 

[Pipingeng100]

If it is under NACE Requirement, then I guess it is a highly corrosive environment.
If it is not, why you are referring NACE MR0175. (Off-shore).

It is not recommended for Nude Bolts and Nuts. It should be coated/plated by Zinc-Ni plated or according to
your specs.

 

[firsan64]

Thanks a lot, friends. I will thinking a little more.

 

[SJones]

The meaning of the ISO 15156-2 statement is that it is not acceptable to use a coating as a means of rendering an unqualified substrate acceptable for H2S service. Since the B7-2HM would be considered as qualified for H2S service, the application of a coating is not restricted.

Steve Jones
Corrosion Management Consultant

http://www.linkedin.com/pub/8/83b/b04

All answers are personal opinions only and are in no way connected with any employer.

 

[KKeong]

Vendor should do a post-bake operation for zinc plated fasteners to prevent hydrogen embrittlement.

Have a look at BS 7371 and Shell ES/313 to have a better idea.

 

[firsan64]

Hello, guys.
Their informations are all that I need to decide to do. Thanks a lot.